The natural teeth of a patient are often lost as a result of dental disease or trauma, making it desirable to replace a natural tooth with a prosthetic device. One type of prosthetic device is the dental endosteal or endosseous implant which is surgically positioned within the mandibular or maxillary alveolar bone of the patient and, after healing, is fitted with a tooth-simulating prosthesis or crown.
One type of dental implant, often called a submergible or two-stage, has a separate root member which is implanted by the oral surgeon in the alveolar bone of the patient. Following healing, a head member is mounted on the root and the crown is then mounted to the head member. This type of implant has met with a substantial degree of success.
Often the alveolar ridge is narrow and/or not aligned with the alignment of the nature teeth. To obtain parallelism with other implants or with the patient's natural teeth, it is necessary to provide implant heads that are on an oblique angle with respect to the root component or with straight heads so that the crown will be aligned with the natural teeth. Fabrication of angled heads is very difficult and the contours at the junction between the head member and the root member are generally awkward and not well adapted for good periodontal management of the gingival tissue at the head interface. It has been necessary to blend the junction of two truncated conical shapes of unlike angles, the axes of which intersect at an angle or don't intersect. This can not be done on a lathe without requiring a fair amount of subsequent hand filing or grinding to blend the junction.
Another way of fabricating these conventional angled heads is to mill them on a computer controlled milling machine. This process requires a rather complicated program as either the upper or lower conical shape can no longer be round in cross section but must elliptical if hand blending is to be avoided. Surface finish is also a problem and machining "chatter" is difficult to avoid.
This junction also becomes the "finish line" for the crown or bridge that subsequently will have to be mounted on this often rather crudely shaped head. This causes the subgingival contours of the head to be imprecise with undesirable overhangs and it becomes more difficult to obtain an acceptable mating of the crown or bridge without gaps and additional overhangs which will contribute to periodontal problems.
It is an object and purpose of the present invention to provide a head member structure which will allow the head member to be easily and relatively inexpensively machined and yet will make an optimum interfacing fit with the tissue.
Additionally, with previously known implants, two problems have been commonly encountered during healing. Conventionally, root members are used which have a connector member portion, such as a tapered post, or large diameter neck which extends up through the gingiva for later attachment to the head member. However, such protruding posts or necks cause problems for the dentist and the patient. The root member should not, if possible, be subjected to loading or forces incident upon it during mastication because such forces will move the implant and thus prevent a tight interlocking healing of the bone against the implant. Such a protruding connecting member also provides a site for infection or other disease problems during the healing process. Most existing "submergible" implants are barely so and often protrude through the tissue or become exposed.
It is an object and feature of the present invention that a root member be provided which is entirely submerged within the bone and does not protrude through the gingiva during healing.
Another difficulty experienced with the use of endosseous implants is the permanent loss of bone at the crest of the alveolar ridge around the root member. The bone may sometimes initially form and then die back to form, a crater or ditch in the bone about the region of the implant.
It is an object and feature of the present invention to provide a root member structure and a method for surgically implanting the root member which promotes the healing of the bone along the extension of the natural contour of the crest of the boney ridge and thus eliminate such a crater and regenerate the natural crestal contour.